Are All Prior Art Are Treated Equally?
Feb 1, 2020

Are All Prior Art Are Treated Equally?

We all know that the existence of "prior art" can be a roadblock to obtaining a patent. Prior art is defined as any evidence that proves your invention is already known. According to EPO, the prior art does not need to exist physically or be commercially available. It is enough that someone, somewhere, sometime previously has described or shown or made something that contains a use of technology that is very similar to your invention.

What are the different types of prior art?

  • Any publication, in any form or medium, in principle qualifies as prior art includes patents and scientific publications, textbooks, newspapers, lectures, demonstrations and exhibitions and any other disclosure.
  • Any products that utilize any feature applied in a patent application, then the product becomes a prior art for the invention.
  • Any oral disclosures, will be considered as prior art, that includes lectures or non-confidential discussions between inventor and third party?

However, some questions may arise here: Are all prior art types considered equally in the examination process or in the invalidation? Do examiners search all types of prior arts in any form during an examination for granting a patent? Are all types of prior art invoked in the same way? For instance, are the patents and catalogs or products available on the market equally important for examiners or in the court during litigation? With considering worldwide search, are all types of prior art in various languages are searched?

To finding the answerers, we shortly look up the available resources achievable via internal. Inappropriately, there is not available enough information to ensure which types of prior art are most likely used by examiners during patent granting and whether prior art in different languages ​​is also fully explored.

However, it can be said that the “time” is a limiting factor for any examiner to explore all variety of prior knowledge for confirming the novelty and inventive step of an application. With this regard, Journal articles and patent documents are more likely to be explored by the examiners during patent granting.

Results of a study by Frakes & Wasserman (2014)  revealed the USPTO examiners are apportioned a pre-determined number of hours to review each application and are effectively compensated under the assumption that they spend that amount of time on the application. The number of hours depends on the technologies of the application. For example, for patent applications in Artificial intelligence, the examination generally takes 31.6 houses. While, examiners with the same experience in the compound tools area (i.e., hammers, wrenches, etc.), are allotted only 13.8 hours.

According to another study conducted by (Frakes & Wasserman) in the same year 2014, an examiner spends only nineteen hours reviewing an application (including reading the patent application, searching for prior art, comparing the prior art with the patent application, writing a rejection, responding to the patent applicant’s arguments, and often conducting an interview with the applicant’s attorney. Therefore, in the examination process, exploring all types of prior art is likely to be impossible.

But what happens if the substantive examination has not considered all types of prior arts and application has been granted. It is possible that

The possible way is the invalidation of the granted patent. Who would try to invalidate the granted patents? If patenting seems to be a threat to the interests of third parties (generally competitors), the third party will promptly file a complaint against the granted patents and seek convincing to substantiate his compliance. Any kind of prior art is any kind of document that anticipates and invalid the granted invention are collected.  

This process is known as the “Opposition” in the European Patent Office and “reexamination” in the US Patent and Trademark Office (USPTO). After approving a patent for a grant, the protesters are given a few months to oppose the invention subject to the grant.  Oppositions can file on many grounds. For example, if the subject of the invention is not patentable or is not consider as a novel invention or it is obvious in the light of prior knowledge.

In Europe, any third party, even in the form of a straw man (anonymously and on behalf of the complainant), can file a post-grant opposition under EPC rules. The results of the examinations either have no effect on the patent granting or withdrawal.

In the US, a nine-month after granting, any third party could file an opposition, which is called inter-parte reexamination. During the patent life, of course, there is still the right to appeal, which is a fully litigious process, and in the USPTO this process is called Ex Parte reexamination, which costs more than the former type for the plaintiff.

Which prior art will be considered during the invalidation process?

 Since no prior study has provided a comprehensive picture of the prior art underlying those district court decisions, Professor Yelderman in one research, analyzed the prior art with a focus on those relied upon by courts in invalidations procedures. In the following paragraphs, we highlight some of his research results that could partly answer some of our questions.

 Professor Yelderman in his research focused on the prior art relied upon by courts when finding claims to be either “anticipated” or “obvious”.  Regarding his article, “anticipation” doctrine is what we call “lack of novelty” requirement”. A patent claim has novelty only when all of the elements of the claim can be found in a single prior art reference. Therefore, the anticipation inquiry is quite straightforward. The factfinder simply compares the prior art to the patent claim to see if there is a match.

The other way that prior art can invalidate a claim is through the “obviousness doctrine”. Even in cases in which the claimed invention is not anticipated, it may be invalid “if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious”. Since Obviousness invalidations can be based on multiple references. Therefore, they are a bit harder to summarize concisely.

Based on Yanderman research result, invalidating prior art could be classified into four categories: U.S. patents (including U.S. patent applications), foreign patents (including applications to foreign patent offices and applications filed under the Patent Cooperation Treaty), printed publications, and activities (including prior uses, sales, and invention by another). Figure 1 illustrates the percentage of obviousness or lake of novelty invalidation events relying on each category of the prior art.

Figure 1: Basic for invalidity (Stephen Yelderman (2018))

As illustrated in Figure 1, the majority of novelty invalidations (52%) relied on prior art classified as activities (solid black columns). in view of obviousness, since 41% of obviousness invalidations involved “mixed” prior art (orange column) means that the court relied on at least one reference in one category and at least one reference in a different category. Therefore, to obtain a clear picture of how courts use prior art to find claims obvious, the cross-category combinations have been used in this study.

Figure 2, illustrates the number of obviousness invalidations citing any art in each category as a percentage of all obviousness invalidations. As shown in the figure, 63% of obviousness invalidations cited at least by one U.S. patent.

FIGURE 2: Basic for invalidity based on obviousness (Stephen Yelderman (2018))

What is the foreign patent, printed publication, and activities role in the novelty and obviousness invalidation?

It seems there is still no evidence of how is the influence of foreign printed publications and activities on invalidation. But Yelderman paid attention to the foreign patent role in the invalidation process. According to this research results, 10% of lack of novelty invalidations relied on foreign patents, and 20% of obviousness invalidations were built-in partial reliance on them. The results revealed that reliance on the foreign patent was almost always partial. In Otherworld, if foreign patents rely on themselves to establish obviousness, their share is only 2% of all obviousness events.

 Therefore, the role of the foreign patent in novelty invalidation is in higher weight than obviousness since each foreign patent could be cited for novelty invalidation.  In novelty invalidation reliance on foreign patent, it is interesting to notice that in over half of the lack of novelty events, involving a foreign patent, the inventor’s own foreign patent was the problem. Similarly, this result could be generalized for foreign activities and printed publications, as inventors her own disclosing before filing, even in a foreign language, could cause a problem. 

As Figure 3 illustrates below, among all reasons for the lack of novelty invalidation events, citing a foreign patent, 56% relied on the inventor’s own foreign patent. The figure illustrates there is not any instance in this study that the defendant’s foreign patent leading to novelty issues for invalidation. The remaining 44% of anticipation events cited a foreign patent with no identified party relationship.

FIGURE 3: Basic for invalidity based on a foreign patent (Stephen Yelderman (2018))


As it is illustrated in figure 1, the majority of novelty invalidations (52%) relied on prior art classified as activities.  prior uses, sales, and earlier invention by someone else are categorized as “activity”. The figure illustrates also that nearly a third (28%) of obviousness events drew at least partially on prior activities. The study results of Yelderman, couldn’t be able to reveal clearly which activities have a higher weight in invalidating the patent. And the incentivizing value of invalidation based on prior activities remains ambiguous. For one, public uses and sales that are undeniably public can still be small scale, such as the sale to a handful of select customers. And even when use or sale was widespread, these activities may not leave the kind of publicly searchable records that a third party could be expected to find years after that activity has ceased.


Due to the time limit of examination in many national patent offices, as examiners are given less time to review applications upon certain types of promotions, the less prior art they search and then cite and the less likely they are to make time-consuming obviousness rejections. Therefore, the more likely they are to grant patents without comprehensive examination and search and cite all types of prior art.

A high percentage of invalidations based on lack of novelty involves the plaintiff or defendant’s own prior work, and it appears that for invalidation based on lack of novelty, reliance on ambiguous prior art is quite rare.

A significant number of obviousness invalidations rely on obscure prior art, suggesting that they may be less likely to provide incentivizing error correction. However, current policies encouraging testing of obviousness may nonetheless be defensible on other grounds and will require further study.

The foreign patent has lower weight in the invalidation process, and the invalidation based on obviousness normally doesn’t occur rely only on the foreign patent. In lack of novelty invalidation which involves foreign patent, the inventor’s own foreign patent was the problem. 



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